https://www.prepaidphonenews.com/2018/10/boost-mobile-quietly-launched-bring.html
Tried a Sprint S4, Note 3, iPhone 5S and two Boost LG Stylo - passed.
Tried a Boost Prestige and Sprint S6, Note 4 - got a bummer message
Interesting results. It sounds like Boost has loosened up a little on what phones can be brought in, and especially what phones qualify for BYOD. Very mixed results, with little visible predictability.
I'm curious-- of the 3 Boost phones you tested, had any of them been on other Sprint MVNOs previously? I'm wondering if this is another 'flag' artifact, with the Prestige still being ID'd in the system as a Boost device, while the Stylos are ID'd as 'white label'.
Not sure, likely the Stylo had been ISU'd by RingPlus.
Tried the Stylo on Sprint 1 yr free, shows as ineligible.
I had the same problem "getting through" the promo process. Even when my unlocked phone passed their online MEID checker, there was no way to continue the process to buy the Boost SIM card, and the fine print for the promo clearly states that the SIM has to be purchased online.
For those who are happy with Sprint coverage, $25 a month for unlimited everything is a killer deal! Hope they fix that website glitch IF they really want signups; at this point it seems like a true Catch-22 to me.
I've seen a couple of reports that there is a discrepancy between the MEID check and the actual "allowed" devices that will be accepted during the signup process. (False positives that won't allow completing the process.)
The link I saw to the 'approved' device list seemed to show the same basic list of multi-carrier phones as the Sprint Unlimited Free offer: I didn't dig too deep, though, since I'm not likely to sign up for the offer.
Same here. I was just checking out the process, and my "unlimited" plan (1GB high speed, then throttled data) with a different carrier is less expensive and has more data than I ever use, so it's no big deal if the Boost promo is a no-go.
Interesting... you would think that if Boost really wanted to add more subscribers, they would make it easier, not more difficult, to sign up for their promo by allowing either online or in-store signups. Oh well, I guess that's part of the fun with MVNOs. 
Diedrich_Duo writes: "Interesting... you would think that if Boost really wanted to add more subscribers, they would make it easier, not more difficult, to sign up for their promo by allowing either online or in-store signups. Oh well, I guess that's part of the fun with MVNOs. :)"
They're trying to walk a fine line between boosting customer numbers, and not cannibalizing their standard rates-- especially important if you're dealing with franchise stores. Like the Sprint promo, they're trying to target those who would not consider signing up at the standard rate, and still getting the typical consumer who needs a little hand-holding to pay the standard price.
Of course, that doesn't explain why the signup process is broken online......